NAV_HEADER_POSITION = 0
NAV_FOOTER_POSITION = 1
NAV_HEADER_SIZE = 5
NAV_FOOTER_SIZE = 10
# 轮播广告显示的最大数量
BANNER_SIZE = 10
# 列表页数据的缓存周期，单位：秒
LIST_PAGE_CACHE_TIME = 60